Alginate is a water-soluble natural polysaccharide macromolecule. A commonly used compound is sodium alginate, which can be extracted from the cell walls of brown algae. Alginate is a linear block copolymer composed of (1-4)-glycosidic linked α-L-guluronate (molecular formula C6H8O6, abbreviated as G) and its stereoscopic isomer β-D-mannuronate (molecular formula C6H8O6, abbreviated as M). The molecular weight of sodium alginate macromolecule ranges from 10,000 to 600,000. Since alginate is an anionic macromolecule, it is easy to form water-insoluble hydrogel by crosslinkage with metallic cations, especially bivalent cations such as calcium ion (Ca2+), barium ion (Ba2+), or zinc ion (Zn2+). Alginate hydrogel is heat-irreversible. The elasticity and stiffness of alginate hydrogel can be adjusted by changing a G/M ratio of the alginate composites.
Since alginate hydrogel is a natural polysaccharide macromolecule, it is extensively used in food, textile and biomedical industries. In the textile and biomedical industries, an alginate fiber made from the alginate hydrogel has a good biocompatibility and ability to chelate heavy metallic cations. Functional fabrics made by adding nutrients or antimicrobial components in the alginate fiber are useful in the field of skin care, cosmetics and medical treatments. For example, since silver ion has a strong antimicrobial activity, a medical dressing made by an alginate fiber containing silver ions provides good anti-inflammatory and protective effects, and thus can promote healing of wounds. Manufacturing methods of alginate fibers containing silver ions mainly include vapour coating, sputter coating, and spinning dope coating silver ions or water-insoluble silver salts on the alginate fibers in post processing. However, silver ions are randomly and unstably scattered about the surface structure of the alginate fiber by the afore-mentioned methods; furthermore, silver ions are also easily deactivated with atmosphere oxidation. Moreover, in order to obtain the best medical effects, the alginate fibers as medical dressing have to be coated with high concentration of silver ions . However, high silver ion content of medical dressing leads to a high risk in biocompatibility and thus is considered not optimal to be used in the human body. Therefore, it is an object of the present invention to provide alginate derivatives, which stably contain low concentration of silver crystallite instead of high concentration of silver ions. Such alginate derivatives can release silver atoms and/or silver ions steadily to effectively destroy pathogen and is safe for human use.